Adding events to your calendar is a great way to remember events you are interested in.  Unfortunatly to add external events to your Outlook 365 web based calendar is troubling at times. Here is how to add a downloaded or sent ics file to your outlook calendar. 

1. Save your .ICS event form the email it was sent from or downloaded to somewhere you can access it on your device/computer's drive. 
   
   
2. Go to O365/OWA Calendar.  
   
   
3. Select Add Calendar from menu. 
   
   

   Click to expand - Select Add Calendar

   
   
   
   
4. Select option "From File"
   
   

   Click to expand - Choose from File

   
   
   
   
5. Navigate to the saved .ICS event file
   
   
6. Make sure the Calendar you are importing is selected in the import form file dialog
   
   

   Click to expand - Select Calendar and Add

   
   
   
   
7. Click SAVE
   
   
8. Event appears on O365/OWA